The other day I was on an AA (Eagle) CR2 that was almost sold out. After boarding was complete, an agent came onboard and told us that they'd have to take 10 people off the flight due to the hot weather and short runway. They asked for volunteers, offering $500 and guaranteed transportation the next day. They also said that if they didn't find enough volunteers, they would take people off in the order of booking (last booked, first off). That seemed odd to me (likely most expensive tickets first?) and I was fully expecting to get called upon since I had only booked the ticket two or three days before the flight. But somehow I "survived". Looking at the CoC now, I see that the documented criteria is different from what was announced (and perhaps more logical): "In such events, American will usually deny boarding based upon check-in time, but we may also consider factors such as severe hardships, fare paid, and status within the AAdvantage® program." I recall reading elsewhere in the past that airlines can use any criteria they want, but have to document it. The AA CoC seems extremely vague here. Does anyone know what other carriers use in practice?